You can 'nudge' people towards behaving in a more responsible way without being aggressive or official. Like footmarks on an escalator that suggest which side you should stand on.

Incidentally, having a set of green footprints marked on the floor leading to a litter bin has been shown to reduce dropped litter by up to 35%.

Humans respond to kindness and they remember kind acts towards them as it's a pleasurable sensation; it encourages a repeat of the same behaviour that led to the reward. Which is why I love this story (see video above) about New Hampshire police officers dishing out citations for good behaviour. And free pizza!

As Bill Murray once said: 'The world is full of nice people. If you can’t find one, be one.'